Dual clutch transmission
of the Volkswagen Group 6-speed dual clutch transmission, the Direct-Shift Gearbox (DSG). The concentric multi-plate clutches have been sectioned, along with the mechatronics module. This also shows the additional power take-off unit for distributing torque to the rear axle for four-wheel drive applications. - View this image with annotations]] A '''dual clutch transmission', commonly abbreviated to DCT (sometimes informally referred to as a twin-clutch gearbox, double clutch transmission, or similar variations thereof), is a differing type of semi-automatic or automated manual automotive transmission. It utilises two separate clutches for odd and even gear sets. It can fundamentally be described as two separate manual transmissions (with their respective clutches) contained within one housing, and working as one unit. They are usually operated in a fully automatic mode, and many also have the ability to allow the driver to manually shift gears, albeit still carried out by the transmission's electro-hydraulics. This type of transmission was invented by Frenchman Adolphe Kégresse just prior to World War II, but he never developed a working model. The first actual DCTs arrived from Porsche in-house development, for Audi and Porsche racing cars in the 1980s, when computers to control the transmission became compact enough: the Porsche Doppelkupplungsgetriebe ( ) (PDK) used in the Porsche 956 and 962 Le Mans race cars from 1983, and the Audi Sport Quattro S1 rally car. A dual clutch transmission eliminates the torque converter as used in conventional epicyclic-geared automatic transmissions. Instead, dual clutch transmissions that are currently on the market primarily use two oil-bathed wet multi-plate clutches, similar to the clutches used in most motorcycles, though dry clutch versions are also available. The first series production road car to be fitted with a DCT was the 2003 Volkswagen Golf Mk4 R32. , the largest number of sales of DCTs in Western Europe are by various marques of the German Volkswagen Group, though this is anticipated to lessen as other transmission makers and vehicle manufacturers make DCTs available in series production automobiles. In 2010, on BMW Canada's website for the 3 Series Coupe, it is described both as a 7-speed double clutch transmission and as a 7-speed automatic transmission. It is actually a dual clutch semi-automatic. Overview In DCTs where the two clutches are arranged concentrically, the larger outer clutch drives the odd numbered gears, whilst the smaller inner clutch drives the even numbered gears. Shifts can be accomplished without interrupting torque distribution to the driven roadwheels, by applying the engine's torque to one clutch at the same time as it is being disconnected from the other clutch. Since alternate gear ratios can pre-select an odd gear on one gear shaft whilst the vehicle is being driven in an even gear, (and vice versa), DCTs are able to shift more quickly than cars equipped with single-clutch automated-manual transmissions (AMTs), a.k.a. single-clutch semi-automatics. Also, with a DCT, shifts can be made more smoothly than with a single-clutch AMT, making a DCT more suitable for conventional road cars. Clutch types There are two fundamental types of clutches utilised in dual-clutch transmissions: either two wet multi-plate clutches which are bathed in oil (for cooling), or two dry single-plate clutches. The wet clutch design is generally used for higher torque engines which can generate and more (the wet multi-plate clutch DCT in the Bugatti Veyron is designed to cope with ), whereas the dry clutch design is generally suitable for smaller vehicles with lower torque outputs up to . However, whilst the dry clutch variants may be limited in torque compared to their wet clutch counterparts, the dry clutch variants offer an increase in fuel efficiency, due to the lack of pumping losses of the transmission fluid in the clutch housing. Clutch installation There are now three variations of clutch installation. The original design used a concentric arrangement, where both clutches shared the same plane when viewed perpendicularly from the transmission input shaft, along the same centre line as the engine crankshaft; when viewed head-on along the length of the input shaft, this makes one clutch noticeably larger than the other. The second implementation utilised two single-plate dry clutches which are side-by-side from the perpendicular view, but again sharing the centre line of the crankshaft. A latest variation uses two separate but identical sized clutches; these are arranged side-by-side when viewed head-on (along the length of the input shaft and crankshaft centre line), and also share the same plane when viewed perpendicularly. This latter clutch arrangement (unlike the other two variations) is driven via a gear from the engine crankshaft. Suppliers BorgWarner BorgWarner Inc. is the current leading worldwide supplier of wet dual clutches and electro-hydraulic control modules (mechatronics) for these dual clutch transmissions, along with complete dual clutch transmission and transaxle assemblies. BorgWarner, who call their technology "DualTronic", entered series production (excludes Bugatti Veyron) for Volkswagen Group, who re-named Direct-Shift Gearbox (DSG) in 2003 in the Volkswagen Golf Mk4 R32. The company signed further agreements with three other (unnamed) European automotive manufacturers to incorporate their components in DCTs. On 14 January 2009, BorgWarner announced the establishment of a joint venture with the China Automobile Development United Investment Co., Ltd. (CDUI) which is owned by twelve leading Chinese automakers. This joint venture will be known as the BorgWarner United Transmission Systems Co., Ltd., and will be located in Dalian, China. The company will produce various dual clutch transmission modules beginning in 2011. The Nissan GT-R uses BorgWarner components which include the dual-clutch module, clutch-control and shift-actuation systems and synchronizer assemblies. Fiat Powertrain Technologies Fiat Powertrain Technologies has developed a dual clutch transmission with Magneti Marelli and BorgWarner. Magneti Marelli delivers the control system which integrates BorgWarner's hydraulic actuation module into its own power and transmission control units. It can handle torque inputs of up to , making it the highest-torque dry clutch application. Its weight of just , complete with oil and transmission control unit, its compact three-shaft architecture, especially axially, allowing it to be installed in a wide range of B- and C-segment vehicles. Fiat Powertrain is an independent company looking to maximize its sales to third party organizations, so the DCCT system is likely to go not just to Chrysler-Jeep, which Fiat now controls, but to outside customers, as well. Getrag Getrag has developed a complete range of DCT transaxles, including 7DCL750, a seven-speed transaxle for mid-engine longitudinal applications, capable of taking more than . Getrag will be providing its DCT in its first commercial applications, for the Dodge Journey and Volvo S40 and V50, from mid-2008. Getrag has the 6DCT250 dry DCT under development, for use in front wheel drive transverse applications, and uses electro-mechanical actuation, rather than electro-hydraulic. In the 2nd quarter of 2008, Getrag had signed an agreement with Chrysler to supply its PowerShift DCTs for use in American markets. However, due to the global economic downturn, this was subsequently cancelled. Getrag is also working with Bosch to develop a DCT for use in hybrid vehicles. Getrag dual clutch transmissions are used in the BMW M3, BMW Z4 Sdrive35i,http://www.autonews.com/apps/pbcs.dll/article?AID=/20091101/CUTAWAY01/910299984/1193# Ferrari California, Ferrari 458 Italia, Mercedes-Benz SLS AMG , Mitsubishi Lancer Evolution X, Mitsubishi Lancer Ralliart, Ford and Renault vehicles. Graziano Italian specialist Graziano Transmissions is in the process of developing a wet clutch DCT for original equipment manufacturer (OEM) fitment into supercars. It aims to be in production by 2010, and will be targeting automakers such as Ferrari, Maserati and Aston Martin. Their DCT is aiming to have a torque handling capacity of , and they are also aiming to improve shift quality over their current automated manual transmissions (AMTs). They currently supply the 7-speed DCT for McLaren's MP4-12C supercar. LuK LuK Clutch Systems, LLC. designed and manufacture the dual dry single plate clutch system for the Volkswagen Group seven-speed DQ200 Direct-Shift Gearbox (DSG) introduced in 2008. This DSG variant is used in smaller cars, with smaller displacement engines with relatively low torque outputs. LuK are naming their technology "XSG" for their overview of automated shift gearbox systems, and "Parallel Shift Gearbox" (PSG) for its own proprietary DCT. Ricardo English specialist consulting engineering company Ricardo plc designed and built the Bugatti Veyron's seven-speed dual wet multi-plate dual clutch transmission, specifically to cope with the of torque generated by the cars' W16 engine. ZF ZF Friedrichshafen AG designed and build with Porsche the two different variants of the Porsche Doppel-Kupplunggetriebe (PDK) seven-speed '7DT' dual wet multi-plate clutch transmission. Applications AUDI Audi co-invented the production-worthy technology with Porsche, and introduced the first volume-production units in 2003 in the VR6 TT, along with the similarly powered VW Golf mentioned. BMW In January 2008, BMW introduced a dual clutch transmission for their M3 model, manufactured by GETRAG, embedding a DualTronic dual clutch module from BorgWarner, and dubbed M Dual Clutch Transmission (M DCT). The same transmission is used in the second generation Z4 (the Sdrive35i version), and is an available option on the 335is and later 135i builds. Chrysler Chrysler is scheduled to receive Fiat Powertrain Technologies C635 dual dry-clutch transmission for use on Chrysler's inline-4 and V6 Pentastar in the Dodge Dart and a D-segment car in 2013. Fiat Group Ferrari incorporated a Getrag designed and manufactured seven-speed dual wet clutch transmission in their California and 458 Italia sportscars. Fiat Powertrain Technologies (FPT) started production of "TCT" Dual Dry Clutch Transmission (DDCT) in early 2010 at the Verrone plant. The C635 DDCT gearbox is used for B (supermini), C (compact car), and D segment (large family car) cars, and can handle torque up to . Fiat's C635 DDCT gearbox was introduced in Alfa Romeo MiTo in 2011. Ford Motor Company Ford Motor Company has released a wet clutch "PowerShift" transmission on the 2008 Ford Focus (international) and Ford C-MAX. This wet clutch DCT was designed with gearbox specialist Getrag under the GETRAG FORD Transmissions joint venture, founded in 2001, and is expected to feature in other Ford and Volvo models. Ford has announced the US-market version of the Mark VI Ford Fiesta coming in 2011 will feature a dry clutch PowerShift transmission. Ford also announced the introduction of PowerShift transmission to North American market by 2010. The Volvo version will be built in Koping, Sweden at Volvo's transmission plant. The PowerShift gearbox will be introduced on the second generation Volvo S60, and then on to the V50 and C30 models. The XC60 is expected to get this Ford PowerShift gearbox along with other new models to make more sporty cars. General Motors In the company's restructuring plan, it revealed that dry dual clutch transmission would be available in 2012 calendar year. The GM's dual-clutch gearbox will be introduced on the GMC Granite. The new front-wheel drive transmission will incorporate the latest innovations for improving fuel economy and performance. The transmission alone will provide upward of 10 percent improvement in fuel economy over today’s conventional six-speed automatic transmissions. The co-developed transmission between GM and SAIC will feature dry, dual-clutch technology. It will provide shift comfort equal to a conventional fully automatic transmission, with superior quality, while reducing CO2 emissions. Honda In October 2009, Honda launched the VFR1200F, a motorcycle with a 1,200 cc V4 engine and optional DCT dubbed the ''Next Generation Transmission. In May 2009, Honda CEO Takeo Fukui mentioned that Honda was working on a new dual clutch transmission system that could be matched with future hybrids. Hyundai At the 2009 Geneva Motor Show, Hyundai unveiled ix-onic concept car, which was said to feature a six-speed dual clutch transmission. On 22 December 2010, Hyundai teased the reveal of its entry-level sports car, the Veloster, a vehicle with a dual-clutch transmission and an estimated fuel consumption of . The teaser notes the date of reveal to be 10 January 2011, when it will be shown at the North American International Auto show. Lotus Lotus Cars has submitted a patent application for a lighter, simpler and more compact dual-clutch transmission system. The gearbox shown in the application is an eight-speed unit, with seven forward gears and reverse. McLaren Automotive McLaren Automotive introduced a seven speed dual clutch on MP4-12C made in Italy by Graziano. The design comes with a feature called "Pre-Cog" which allows the driver to preselect the next highest or lowest gear decreasing shift times. Mercedes-Benz The Mercedes SLS AMG use a Getrag AMG 'SpeedShift' seven-speed dual clutch gearbox, mounted at the rear in a transaxle configuration, and connected to the engine via a carbon fibre driveshaft enclosed in an aluminium torque tube. According to Mercedes-Benz, it is capable of gear changes in as little as 100 ms. The SLS and the Ferrari California share the same DCT unit.Jeremy Clarkson "The Italian Job" DVD (0:59:19 - 0:59:31) Mitsubishi The Mitsubishi Motors Lancer Evolution X and Lancer Ralliart are supplied with Mitsubishi's Twin Clutch SST (abbreviated TC-SST, for "Twin Clutch Sport Shift Transmission" or "Twin Clutch Sportronic Shift Transmission") dual clutch transmission, controllable by steering wheel mounted magnesium paddle shifters. It is the Getrag-built, PowerShift 6DCT470 transmission in the Mitsubishi Lancer Evolution. Mitsubishi Fuso Truck and Bus Corporation The Mitsubishi Fuso Truck and Bus Corporation presented a world first with a double-clutch transmission for commercial vehicles. The new six-speed M038S6 "Duonic transmission" features wet clutches and incorporates the ability to creep in traffic for smoother operation. Although Duonic-equipped trucks will probably be driven mostly in fully automatic mode, the transmission can also be manually shifted. Nissan The Nissan GT-R's rear transaxle six-speed dual clutch transmission also contains the differential for the car's all-wheel drive (AWD) system. The dual clutch system was built by BorgWarner, partnered with Nissan's gearbox supplier Aichi Machine Industry, and weighs a total installed mass of . Code named the GR6, the transmission is quite durable being able to hold in excess of 600 ft-lbs of torque. Nissan reports shift times of 200 milliseconds. PSA Peugeot Citroën PSA has dual clutch transmission in Peugeot 4007 and Citroen C-Crosser CUVs, produced by Mitsubishi motors. Porsche Porsche AG offers a series production of two new longitudinally installed, ZF Friedrichshafen AG designed and built with Porsche '7DT' wet-clutch versions of its previously race-only Porsche Doppelkupplungsgetriebe (PDK) transmission. The first variant, the 7DT-45, is used on its 2009 997 Carrera and Carrera S models. This version is also offered on the 2009 Cayman, Boxster It uses a ZF Sachs ND2015 clutch pack, and has a torque handling capacity of . A higher torque version of the same transmission, the 7DT-70, is also available for the 2010 911 Turbo. This is rated at , and uses a different ZF Sachs clutch - the ND2216. The second PDK variant, the 7DT-75, is available on the 2009 Panamera. This is constructed fundamentally different to the 7DT-45/7DT-70 versions; in that the internal shafts are mounted above the input shaft, so as to achieve a lower centre of gravity for the Panamera. It also uses just one oil circuit, whereas the 7DT-45/7DT-70 use two separate circuits; with very different specifications of fluids needed. Both fundamental variants use seven forward speeds, and Porsche claim the Doppelkupplung PDK transmission will replace the outgoing conventional Tiptronic automatic transmissions. However, other reliable industry sources state that Porsche still intends to use conventional automatics; with the eight-speed ZF 8HP being cited. Like all DCTs, the Porsche PDK transmission is fundamentally two separate manual transmissions in one. With the 1st, 3rd, 5th, and 7th gears and reverse available on one shaft, and 2nd, 4th, and 6th gears available on the other shaft. Porsche claim noteworthy improvements in CO2 emissions of around 15% when comparing DCT installations against its former automatic transmission, of which a half can be directly attributed to the DCT. And when compared directly with a manual transmission; 16% improvement can be directly attributed to the DCT. Renault Renault will be introducing a new six-speed dual dry clutch DCT in the early part of 2010. This will initially be made available on the New Mégane with the dCi 110 DPF engine. The DCT system was built by Getrag. This will enable these DCT-equipped Meganes to be the marque's first automatic cars to qualify for the Renault eco² signature. Volkswagen Group Volkswagen Group produces DCTs under the Direct-Shift Gearbox (DSG) name, from the . It is used in all of their mainstream marques, including Volkswagen Passenger Cars, Audi, SEAT, Škoda, and Volkswagen Commercial Vehicles, and also its top-tier marque Bugatti. Audi originally used the Direct-Shift Gearbox (DSG) name, it now uses the name "S tronic" for its DCTs. The first ever worldwide series production DCT was the Volkswagen Group DQ250 six-speed dual clutch transmission, with dual concentric wet multi-plate clutches. It was produced at the Group's Kassel plant under exclusive license from Borg-Warner for use in transverse powertrain installations, of either front-wheel drive or four-wheel drive (4WD) layouts. The 4WD versions are fundamentally identical to the 2WD versions, but the 4WD versions use an additional bolt-on power take-off unit to direct engine torque to the Haldex Traction rear axle. This DQ250 variant is used in a wide range of models: Volkswagen Passenger Cars (Polo, Golf/Rabbit/Golf Plus, Scirocco, Jetta, Eos, Passat and Touran); Audi cars (A3, and TT); SEAT cars (Ibiza, León, Altea and Toledo); Škoda cars (Octavia and Superb); and Volkswagen Commercial Vehicles (Caddy and T5 Transporter). A second variant of the Direct-Shift Gearbox went into series production in 2008 – the DQ200. This consists of seven forward ratios, but the notable difference over the original DQ250 is the change from wet- to dry-clutches. This variant uses two single-plate dry clutches, arranged in a tandem design (instead of concentrically) and are therefore similar in size. The DQ200 is again for use in transverse applications, but is intended for use in smaller cars, with smaller displacement engines that generate relatively low torque outputs. When used in the latest Golf with the engine, this new 7-speed DSG uses roughly 6% (5.9l/100 km for the 7-speed DSG compared to 6.3l/100 km with the manual) less fuel than the same engine with a manual transmission and up to 20% less than a conventional automatic transmission. The original DQ250 also remains available. Volkswagen Group subsidiary Audi AG have also developed an all-new DCT - the DL501, for use in longitudinal powertrains. Like the original transverse DQ250, this DL501 utilises dual wet multi-plate clutches, but unlike the DQ250, this variant uses seven forward ratios. This DL501 variant made its debut in the Q5, and also is used in the latest versions of the A4 (B8) and S4 (B8). It is also be considered for use in an all new A6. Lamborghini, although owned by Volkswagen Group subsidiary Audi AG, does not use a dual clutch transmission; it has a robotised single clutch electrohydraulic manual transmission called "E gear", which is identical to the Audi R8 "R tronic" transmission. English specialist consulting engineering company Ricardo plc produces the seven-speed DCT for the 2005 Bugatti Veyron EB 16.4. Railcar use A different type of dual-clutch transmission has been used in some railcars. The two clutches are placed one on the gearbox input shaft and the other on the gearbox output shaft. When a gearchange is to be made, both clutches are disengaged simultaneously and a brake is applied inside the gearbox. The gearchange is made with all gears stationary, so no synchronizing mechanism is needed. After the gearchange, both clutches are re-engaged. There would be a significant break in transmission so this system would be unsuitable for shunting locomotives. References Category:Automotive transmission technologies Category:Auto parts